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CVE-2026-73420 (GCVE-0-2026-73420)

Vulnerability from cvelistv5 – Published: 2026-08-13 22:04 – Updated: 2026-08-14 15:06
VLAI
Title
NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass
Summary
NextAuth.js provides authentication for Next.js. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the defaultNormalizer used by the email and magic-link sign-in flow validates an address before applying Unicode normalization. An address can contain a Unicode character such as U+FF20 FULLWIDTH COMMERCIAL AT that is not ASCII at-sign but canonicalizes to an ASCII at-sign under NFKC or NFKD normalization. The address passes the normalizer's single-at-sign check, but a downstream sendVerificationRequest mail library or delivery service that normalizes the address can then see two at-sign separators and deliver the passwordless sign-in link to an attacker-controlled recipient. Applications are affected when the email provider uses the built-in normalizer rather than a custom normalizeIdentifier and the downstream sender applies Unicode normalization. An attacker who knows a victim's email address can request the misrouted magic link and sign in as the victim without victim interaction. This issue is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32.
Severity
9.1 (Critical)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-14 15:05 UTC
CWE
  • CWE-180 - Incorrect Behavior Order: Validate Before Canonicalize
Assigner
References
Impacted products
Vendor Product Version CPE status
nextauthjs next-auth Affected: < 4.24.15
Affected: >= 5.0.0-beta.4, < 5.0.0-beta.32
guessed Create a notification for this product.
@auth core Affected: >= 0.1.0, < 0.41.3
guessed Create a notification for this product.
Show details on NVD website
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